Do Fetuses Go to the Bathroom in the Womb?

Yes. Just a couple of months into their development, little humans begin peeing freely into the amniotic fluid that surrounds them in the womb. Then, foreshadowing all the gross stuff that babies do once they’re born, they’ll consume that urine as they swallow the amniotic fluid. Every last one of us has spent several months drinking our own pee. Yay.

In utero pooping is less common. Fetuses get their nutrients from food that their mothers’ digestive systems have broken down, and the waste from that food stays with mom and is taken care of on her end (Thanks, Mom!). Fetuses do ingest some stuff—mucus, bile, fine fetal hairs called lanugo, cells lining the inside of the womb—that needs to get disposed of, though. All this stuff gets broken down by the fetus’s digestive system and forms a viscous, sticky mass of feces called meconium.

Unlike every other poop you’ll produce in your life, meconium is almost odorless and mostly sterile. It usually stays in fetuses’ bowels until they’re born, but some kids—around 13 percent—just can’t wait, and let it loose in the womb. This can be a problem, since feces is now floating in the amniotic fluid that the fetus swallows and takes into its lungs, and “meconium-stained amniotic fluid,” as the docs call it, can lead to serious respiratory distress.